Tuberculosis (TB) was one of the first infectious diseases to be identified. More than fifty years of research has been directed to controlling and eliminating this disease. However, the eradication of TB is still one of the most prominent challenges for basic and clinical research scientists.
Once thought to be under control, TB case reports in the U.S. increased sharply in the early 1990's. Although, this trend has reversed and the reported numbers of new cases has steadily declined in industrialized countries, TB remains a major global public health threat. Recent statistics from the WHO estimate that there are approximately 8.4 million new cases every year with a global mortality rate of 23% or approximately 2 million deaths per year.
Poor chemotherapeutics and inadequate local-control programs contribute to the inability to manage TB and lead to the emergence of drug resistant strains of the bacteria that cause Mycobacterium tuberculosis (Mtb). A survey conducted at 58 international sites between 1996 and 1999 found exceptionally high rates of single and multidrug-resistant strains in Estonia, Latvia and Russia, and revealed that countries such as China and Iran were developing a high prevalence of multidrug-resistance (MDR-TB). See Kruuner, A., Sillastu, H., Danilovitsh, M., Levina, K., Svenson, S. B., Kallenius, G., and Hoffner, S. E. (1998) Drug resistant tuberculosis in Estonia, Int J Tuberc Lung Dis 2, 130-3. Significantly, MDR-TB is much more difficult to treat than sensitive TB, requiring administration of more expensive, second-line antibiotics for up to two years. The frequency of resistance to at least one of the first-line TB drugs (isoniazid (INH), rifampicin (RIF), pyrazinamide or ethambutol) ranged from 1.7% in Uruguay to 36.9% in Estonia. The frequency of resistance is indicative of the global problem involving not only the spread of Mtb, but also treatment.
Finally, of critical importance is the role of TB as a major opportunistic pathogen in patients with HIV/AIDS. Consequently, there is a pressing need for the development of novel TB drugs that are effective against both sensitive and resistant Mtb strains.
Likewise, new drugs are needed to treat patients infected by Francisella tulerensis, the bacteria which causes tularemia. Tularemia is primarily enzootic, however, in humans, it causes lesions and flu-like symptoms. Finding new methods of treating F. tulerensis is of great importance because it is one of the most pathogenic microorganisms presently known. As such, it is currently listed as a category A select agent by the Centers for Disease Control and Prevention because of its potential as a bioterrorism agent.